1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Red shift photons: where does the energy come from?

  1. Jan 25, 2010 #1
    The photon energy is given by E = h*f.

    Now, i am aware of the dual wave/particle character of photons. But let's say i emit ONE SINGLE photon, when moving at, say, 0.99c towards the observer. The observer will observe a huge blue shift in this photon. In fact, with respect to the source, it could be in the radio frequency, yet the observer could see a gamma ray because of the blue shift (the 0.99c is just an arbitrary number - i'm sure there's a certain velocity where this case applies).

    So, i'm the observer, at earth, receiving a photon (gamma ray). This is a high energy photon. Yet, when it was emitted, it was a low energy radio wave. Where does this energy come from? The kinetic energy of the source? If so, where does the energy come from in case it was a photon emitted near a black hole and barely managed to escape, with a huge redshift? (okay, energy loss in that case, to overcome the gravity?)
     
  2. jcsd
  3. Jan 25, 2010 #2
    yes, it's called gravitational redshift.
    http://en.wikipedia.org/wiki/Gravitational_redshift" [Broken]
     
    Last edited by a moderator: May 4, 2017
  4. Jan 25, 2010 #3
    Thanks a lot Vin !
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Red shift photons: where does the energy come from?
Loading...